A widely adopted approach to end-of-life ethical questions fails to make explicit certain crucial metaphysical ideas entailed by it and when those ideas are clarified, then it can be shown to be inadequate. These metaphysical themes cluster around the notions of personal identity, personhood and humanness, and the metaphysics of substance. In order to clarify and critique the approach just mentioned, I focus on the writings of Robert N. Wennberg as a paradigm case by, first, stating his views of personal identity, humanness, personhood, and the relations among them; second, offering a comparison of a view of humans as substances (understood in the classic interpretation of Aristotle and Aquinas) vs. a view of humans as property-things; third, applying the metaphysical distinctions surfaced in the second section towards a critique of Wennberg